Process for the production of metal electrodeposits



3,030,283 PROCESS FOR THE PRODUCTIUN F METAL ELECTRODEPOSITS Wennemar Strauss, Dusseldorf-Benrath, Wolfgang Gundel, Duseldorf-Oberkassel, Alfred Kirstahler, Dusseldorf, and Wolf-Dieter Willmund, Dusseldorf-Holthausen,-Germany, assignors to Dehydag, Deutsche Hydrierwerke G.m.b.H., Dusseldorf, Germany, a corporation of Germany No Drawing. Filed May 15, 1958, Ser. No. 735,360 Claims priority, application Germany Mar. 13, 1954 Claims. (Cl. 204-52) This invention relates to a process for producing metal electrodeposits, and more particularly to additives for copper electroplating baths which are capable of eliminating the adverse effects of impurities in such baths upon the quality of the metal deposits produced by means of such baths.

It is known that copper electroplates which exhibit a so-called semi-brightness can be produced with the aid of customary brightening agents, such as thiourea. As we have disclosed in our prior applications, namely Ser. No. 442,199, now Patent No. 2,849,351, and to a certain extent Ser. No. 464,638, now Patent No. 2,830,014, there are brightening agents which, in contrast to the known brightening gagents, produce electroplates which exhibit full brightness; that is, electroplates which can be further utilized directly without subsequent polishing. These brightening agents are the sulfonic acid derivatives of compounds containing sulfur, nitrogen or oxygen atoms. We have now found that this full brightness is achieved in its best form only if the copper baths are compounded with distilled water and if chemically pure copper salts are used, which is not customary in industry, especially since impurities are always introduced into these baths under conditions of industrial operation. If these highgrade brightening agents are used in electroplating baths which have been compounded with technical-grade tap water-that is, water which contains calcium and magnesium ions-and which contain the customary technicaltent as substances which reduce the qualities of electrodeposits produced from such baths.

Still another objects of our invention is to provide additives for copper electroplating baths which will overcome the adverse effects of inorganic impurities contained in such baths on the brightness of the metal electrodeposited therefrom.

Other objects and advantages will become apparent as the description of our invention proceeds.

We have found that the adverse efiect of inorganic impurities upon the qualities of electrodeposits produced 3,030,283 Patented Apr. 17, 1962 ICC from copper electroplating baths containing, in addition, sulfonic acid brighteners, can be eliminated by adding small amounts of amino compounds free from carboxyl groups to the electroplating bath. Compounds which are added according to our invention have the general structural formula wherein R R R and R are hydrogen or hydrocarbon radicals, and X is a bivalent acylic or cyclic hydrocarbon radical or a heterocyclic ring system which includes one or both of the nitrogen atoms. The hydrocarbon radicals above refer-red to may also include heteroatoms, such as oxygen, sulfur or nitrogen, as well as heteroatom groups derived therefrom. Furthermore, the above hydrocarbon radicals may also have substituents containing oxygen, sulfur or nitrogen atoms.

Other compounds which can be added to electroplating baths containing inorganic impurities of the types referred to above in order to render such impurities inettective as interfering substances are those which contain a =NN= or N=N group.

Still other compounds which, when added to electroplating baths, will render inorganic impurities in the baths impotent as interfering substances in accordance with our invention are heterocyclic compounds which contain two nitrogen atoms in the molecule of a fiveor six-membered ring system, and their derivatives.

The additives of our invention may be used with a number of sulfonic acid brightening compounds which have been completely described in my copending application Ser. No. 442,199, now Patent No. 2,849,351. A number of examples of these compounds are shown in Table 1. These are brighteners which produce copper electrodeposits of a brightness requiring no further polishing. These brightening compounds are generally used in the quantity of 0.01 to 20 grams per liter of electroplating bath.

Table 1 acid-n-propylester-w-sodi- (l1) N-hydroXyethyl-dithiocarbamic acid-n-propylesterw-sodium sulfonate (12) N,N-pentarnethylene-dithiocarbamic acid-n-propylester-w-sodium sulfonate (l3) N-piperazino-dithioformic acid-n-propylester-w-sdium sulfonate (14) 2-mercaptobenzothiazole-S-propane-w-sodium sulfonate (15 S-phenyl-trithiocarbonic acid-S-propane w sodium sulfonate (16) Isothiourea-S-butanew-sulfOnic acid (17) S-phenyl-l,3,4-oxdiazolyl 2 mercaptopropane-wpotassium sulfonate In place of the -n-propylester-w-sulfonic acid radicals, the above compounds may also contain the following:

radicals:

(a) -Ethylester-w-sodium sulfonate (b) -Butylester-w-sodium sulfonate (c) -2-hydroxypropylester-w-sodium sulfonate (d) -2-chloropropylester-w-sodium sulfonate (e) -Isopropylester-w-sodium sulfonate (f) -Benzylester sodium sulfonate Examples of the compounds which are added according to our invention to prevent the adverse efiects of impurities on bright copper electrodeposits are set forth in Table 2.

Table 2 (1) Ethylene diamine (2) N,N-diethyl-ethylenediamine (3) N,N,N,N'-tetraethyl-ethylenediamine (4) N,N'-diphenyl-ethylenediamine (5) N,N'-diethanol-ethylenedianiine (6) N,N,N',N'-tetraethanol-ethylenediamine (7) 1,3-propylenediamine (8) 1,4-tetramethylenediamine (9) 1,6-hexamethylenediamine (10) Diethylenetriarnine 1 l Triethlenetetramine 2.) Hydrazine (13) Phenylhydrazine (14) Azobenzene 15) 1,2-phenylenediamine (16) 1,4-phenylenediamine 17) 1,4-naphthylenediamine (18) 4-amino-diphenylamine (19) 4,4'-diamino-diphenylamine (20) 4,4-diamine-diphenylmethane (21) Benzidine (22). 2-arninopyridine (23) 4-aminopyridine (24) 2-anilino-pyridine (25) 4-amino-quinoline (26) 4-amino-lipidiue (27) 3-amino-carbazole (28) 3,7-dimethyl-3,G-diamino-acridine (29) Pyrazine (30) 2,5-dimethylpyrazine (31) 2,5-diphenylpyrazine (32) Quinoxaline (33) Phenazine (34) Piperazine (35) Z-methylpiperazine (36) 2,5-dimethylpiperazine (37) N,N'-diethylpiperazine (38) N,N'-dihydroxymethylpiperazine (39) N,N'-dihydroxyethylpiperazine (40) N,N'-diphenylpiperazine (41) 2,5-diketopiperazine (42) N,N-diethyl-2,S-diketopiperazine (43) N,N-dibenzylpiperazine (44) Pyridazine (45) 3-methylpyridazine (46) 3-phenylpyridazine (47) Diketotetrahydropyridazine (maleic acid hydrazide) 4 Phthalazine (4,5-benzopyridazine) Cinnoline (5,6-benzopyridazine) Phthalazone Pyrirnidine 2,4-dimethyl-6-aminopyrimidine 2,6-dihydroxypyrimidine (Uracil) 2,4,6-trihydroxypyrimidine 1,3-diphenylhexahydropyrimidine Quinazoline 3,4-dihydroquinazoline Tetrahydroquinazoline Pyrazole l-phenylpyrazole Glyoxaline Z-methylimidazole Benzimidazole Z-phenylbenzimidazole 1,3-bis-( diethylamino) -propanol-2 1,3-bis-(dipropylamino)-propano1-2 1,3-bis-(diisopropylamino)-propanol-2 1,3-bis-(dibutylamino)-propanol-2 1-diethylamino-2-methyl-dodecyl-amino-propanol-Z 1-diethylamino-3-dodecylamino-propanol-2 1-mcthylanilino-3-diethylamino-propanol-2 1-methylanilino-3-piperidino-propano1-2 1-methylanilino3-morpholino-propanol-2 1-cyc1ohexylarnino-3-diethylamino-propanol-2 1,3-bis-(cyclohexylamino)-propanol-2 (76) 1-dicyclohexyl-amino-3-diethylamino-propanol-2 (77 1 dicyclohexyl amino 3 cyclhexylamino propanol-2 (78) 1,3-bis- (dicycloheXyl-amino -propanol-2 (79) 1,3-bis-(methyl-ethyl-amino)-propanol-2 1,3-bisethylamino -propano1-2 (81) 1,3 -bis- (methylamino -propanol-2 (82) N,N'-bis bis (3-diethylanrino-Z-hydroxy-propyl)- piperazine When any of the compounds from- Table 2 or mixtures thereof are added to copper electroplating baths containing sulfonic acid brightening agents, electrodeposits produced thereby are bright and lustrous despite the fact that the bath contains impurities of the type described above, such as impurities which cause hardness, etc. Such bright deposits are obtained over the entire efiective range of current densities. In addition, these additives have the further advantage that they increase the ductility of the electrodeposits.

The amounts in which the additives in accordance with our invention can be added to produce the desired eifect range from about 0.01 gm./liter of bath to about 20 gm./liter of bath, but the preferred amount is from 3 to 12 gm./ liter of bath. The precise amounts required vary from one additive to the other and are also dependent upon the type of brightening agent employed and the amount and kind of inorganic impurities present in the bath. In general, objects can be electroplated in such baths at temperatures ranging from 30 C. to 60 C., and with current densities ranging from 0.5 to 15 amp./dm.

While the theory of the action of such additives in baths containing impurities of the nature described is not fully understood, it has been found that they do not function as softening agents in the usual sense and cannot be replaced by the typical water-softening substances such as sequestering agents and detergents. Nevertheless, they are capable of completely eliminating the disturbing effects of magnesium and calcium ions, introduced by the tap water, and of ferric ions, introduced by the technical grade metal salts used to prepare the electroplating baths, during the electroplating process. It is believed that their effectiveness comes into play on the metal surface of the objects being electroplated, which is indicated by the high concentrations which are required in some instances to produce the desired effect.

The use of the additives in accordance with our invention does not require any change in the composition of the electroplating baths commonly used, nor does it require any change in the conditions under which objects are usually electroplated, particularly with respect to the temperature of the plating bath and the current densities usually employed. In the form of amines the additives we use are soluble in the usual acid copperplating baths containing the usual copper salts in an acid aqueous solution. The additives are not decomposed during the electroplating process.

The above-described additives for electroplating baths in accordance with our invention can be used in con junction with any copper electroplating bath containing a sulfonic acid brightening agent and in which the quality of the metal electrodeposits produced therefrom are adversely affected by impurities of the type described. Various combinations of brightening agents and the additives of the invention may be made. Table 3 sets forth a number of specific examples of such combinations.

The examples of Table 3 will enable persons skilled in the art to understand our invention more completely. However, it will be understood that there is no intention on our part of limiting our invention to these examples.

Table 3 In an acid copper bath which contains 100-240 gm./ liter CuSO .5H O and 10-100 gm./liter H SO the following combinations of brightening agent and diamino compounds free from carboxyl groups are used to produce full bright copper electrodeposits:

Agent of Preferred Agent of Preferred Combination N 0. Table 1, Ooncen- Table 2, Concen- No. tration, No. tration,

gun/liter gmJliter 120 0.5 65 5.0 14 1. 5 2 6.0 4!) 0. 5 6 4. 1 0.8 39 7.0 16 2.0 10 5. 0 7b 0. 13 4. 0 1b 0.25 9 6.0 10 0.1 67 O. 25 0.25 65 0. 3 6f 0. 2 68 0. 2 46 0.1 75 0.1 111 0.05 80 0.6 1a 0.05 69 0. 1 17a 0 03 74 0.1 158 0.25 79 0.5

1a 0.05 82 0.05 1a 07 1 5s 0. 8e 0. 1 38 2.00 0.05 55 0.2 9 0.2 40 0.5 13 0. 25 65 0. 7 2a 0.05 72 0. 1 1e 0.05 81 1. 2

Objects electroplated according to the baths the examples over wide ranges of current densities were provided with a highly lustrous, very bright, adherent and ductile copper plate. These copper plates are much improved over those obtained with the use of the brightening compounds alone.

While we have disclosed certain specific embodiments of our invention, we wish it to be understood that various changes and modifications may be made without departing from the spirit of our invention or the scope of the appended claims.

This application is a cont-innation-in-part of our previous application Ser. No. 458,984, filed September 28, 1954, now abandoned.

We claim:

1. In a process of producing bright copper electrodeposits from acid copper electroplating baths containing impurities found in hard water and in technical grade metal salts, and containing a sulfonic acid brightening agent, the step which comprises adding to such electroplating baths 0.01 to 20 g./l. of an amino compound free 6 from carboxyl groups having the general structural formula wherein X is an organic radical selected from the group consisting of bivalent acyclic hydrocarbon radicals, bivalent cyclic hydrocarbon radicals, and heterocyclic hydrocarbon radicals which include at least one of the nitrogen'atoms, and R 'R R and R are selected from the group consisting of hydrogen, substituted hydrocarbon radicals and unsubstituted hydrocarbon radicals, whereby said impurities are prevented from interfering with the production of bright metal electrodeposits.

2. In a process of producing bright copper electrodeposits from acid copper electroplating baths containing impurities found in hard water and in technical grade copper sulfate, and containing a sulfonic acid brightening agent, the step which comprises adding to such electroplating baths 0.01 to 20 g./l. of l,3-bis-(diethylamino)- propanol-Z, whereby said impurities are prevented from interfering with the production of bright copper electrodeposits.

3. In a process of producing bright copper electrodeposits from acid copper electroplating baths containing impurities found in hard water and in technical grade copper sulfate and containing N,N'-pentarnethylene-dithiocarbamic acid-n-butylester-w-sodium sulfonate as a brightening agent, the step which comprises adding to such electroplating baths 0.01 to 20 g./l. of 1,3-bis-(diethylamino)-propanol-2, whereby said impurities are prevented from interfering with the production of bright copper electrodeposits.

4. In a process of producing bright copper electrodeposits from acid copper electroplating baths containing impurities found in hard water and in technical grade copper sulfate and containing Z-mercapto-benzothiazole- S-propane-w-sodium sulfonate as a brightening agent, the step which comprises adding to such electroplating baths 0.01 to 20 g./l. of 1,3-bis-(diethylamino)-propanol-2, whereby said impurities are prevented from interfering with the production of bright copper electrodeposits.

5. In a process of producing bright copper electrodeposits from acid copper electroplating baths containing impurities found in hard water and in technical grade copper sulfate and containing N,N-dimethyl-dithiocarbamic acid-n-butyl ester-w-sodium sulfonate as a brightening agent, the step which comprises adding to such electroplating baths 0.01 to 20 g./l. of l,3-bis-(diethylamino)- propanol 2, whereby said impurities are prevented from interfering with the production of bright copper electrodeposits.

6. In a process of producing bright copper electrodeposits from acid copper electroplating baths containing impurities found in hard water and technical grade copper sulfate and containing a sulfonic acid brightening agent, the step which comprises adding 0.01 to 20 g./l. of N,N-diethyl-ethylenediamine to such electroplating baths, whereby said impurities are prevented from interfering with the production of bright copper electrodeposits.

7. In a process of producing bright copper electrodeposits from acid copper electroplating baths containing impurities found in hard water and technical grade copper sulfate and containing a sulfonic acid brightening agent, the step which comprises adding to such electroplating baths 0.01 to 20 g./l. of N,N,N,N-tetraethanol-ethylenediamino, whereby said impurities are prevented from interfering with the production of bright copper electrodeposits.

8. The process of claim 1 wherein the compound added to counteract impurities in the electroplating bath is 1,6- hexamethylene diamine.

9. The process of claim 1 wherein the compound added to counteract impurities in the electroplating bath is 1,3- bis- (diethylamino) -prop ano1-2.

10. The process of claim 1 wherein the compound added to counteract impurities in the electroplating bath is N,N'-dihydroXyethyl-piperazine.

References Cited in the file of this patent UNITED STATES PATENTS 2,195,454- Greenspan Apr. 2, 1 940 2,355,070 Harford Aug. 8, 1944 8 Gundel June 3, 1958 Gundel Aug. 26, 1958 FOREIGN PATENTS I France Mar. 5, 1956 ermany Sept. 3, 1953 Great Britain Mar. 21, 1939 OTHER REFERENCES Transactions Electrochemical see, vol. 71 1937); pp;

Transactions Electrochemical sac, Vol 73 (1938), pp.- 

1. IN A PROCESS OF PRODUCING BRIGHT COPPER ELECTRODEPOSITS FROM ACID COPPER ELECTROPLATING BATHS CONTAINING IMPURITIES FOUND IN HARD WATER AND IN TECHNICAL GRADE METAL SALTS, AND CONTAINING A SULFONIC ACID BRIGHTENING AGENT, THE STEP WHICH COMPRISES ADDING TO SUCH ELECTROPLATING BATHS 0.01 TO 20 G/L. OF AN AMINO COMPOUND FREE FROM CARBOXYL GROUPS HAVING THE GENERAL STRUCTURAL FORMULA 